1. Field of the Invention
The present invention relates to an intake apparatus for an internal combustion engine and, more particularly, to an intake apparatus for an in-line internal combustion engine having a surge tank mounted with a throttle body. The invention relates specifically to air in-line ICE, that is, one in which the cylinders are arrayed in a common straight line as opposed to a V-type ICE where the cylinders are arrayed in two rows with the medial axial planes of the cylinders forming a Vee.
2. Description of the Prior Art
A conventional in-line internal combustion engine has a surge tank mounted with a throttle body secured to one side of the surge tank in its intake passage. For example, Japanese Unexamined Utility Model Publication No. 60(1985)-171955 discloses such an intake apparatus. The surge tank and throttle body are connected at common registering surfaces. However, the common registering connecting surfaces of the surge tank and throttle body lie in a plane parallel to a vertical plane passing through the longitudinal axes of the in-line cylinders accommodated in the engine body. Such an arrangement for an in-line engine is inherently unable to satisfy a demand for increased vibration durability. An intake apparatus having a throttle body as described is generally apt to vibrate during the engine operation due to the heavy weight of the throttle body. The vibration occurs mainly in a vertical plane parallel to the axes of cylinders. Consequently, substantially all of the vibration forces are changed into shear stress which acts on the connecting surfaces between the surge tank with the throttle body. Accordingly, problems may be experienced with the sealing between the throttle body and the surge tank. Also, movement of the throttle valves may become stiff.